You don't want to add 5 week old chicks to adults, they will probably get picked on and may even get killed, it is best to wait until the chickens are about the same size (so around four months old for standard birds), and then a long period of seeing but no touching through wire seem to work best, ie dividing the coop into two sections or keeping the new/younger ones in a cage inside the coup for a couple of weeks to a month at least. The chickens will get to know each other and sort of work out a pecking order before actually coming in contact with each other. If you can, letting them free range together is a good idea and should help with the integrating ... It will take a couple of weeks to get the pecking order sorted out when you do combine them. There is a nice article in the Learning Center on integrating flocks you might like to check out, the part about actually combining them is after the quarantine section https://www.backyardchickens.com/a/adding-to-your-flock

A rooster might try to mate with the chicks. Some roos are very nice to young chicks and actually show they around and help them know all the rules. It really depends on your roo.
How old is your roo and your hens?

I think Phoenix Boy may have accidentally posted his question about adding more hens on this thread instead of starting a new thread. Maybe I'm wrong, but I thought this thread used to be about "What Chickens are the most broody?" If I'm wrong, please forgive me and then excuse me while I go get my head checked...lol !!!